The present invention relates to a machine tool featuring a number of machining heads for machining printed circuit boards.
To meet the increasing demand for printed circuit boards in the manufacture of various types of electronic equipment, machine tools have been devised featuring a number of machining heads operating in parallel on respective packs of boards. As is known printed circuit boards are normally rectangular, often of standard size with a long and a short side, and are arranged in packs with locating pins.
Various types of multiple-head machine tools are known, in which the packs of boards are set up on a table movable in a first direction or along a first axis, the heads are movable on a crosspiece along a second axis, and the packs are arranged with the short side parallel to the traveling direction of the heads. Machines of this sort present the drawback of being excessively wide when equipped with more than four heads.
For example, one known machine for machining maximum 570.times.720 mm packs has been equipped with six heads, which means a crosspiece of at least 4000 mm and a total width of about 5000 mm. As these dimensions also involve appropriate sizing of the support, guide and drive members, six heads are considered the absolute limit, and invariably result in a machine of enormous weight, high production cost and poor machining precision.
U.S. Pat. No. 5,230,685 relates to a printed circuit board machine tool featuring two rows of machining heads supported on two parallel crosspieces. For boards of the above maximum size, however, the corresponding worktable must travel about 1500 mm, thus making the machine excessively wide. Moreover, as the packs machined by the second row of heads are practically impossible to load manually from the front of the machine, the table must also be accessible from the rear, thus requiring considerable extra floor space.